The present invention relates to an electronic module for the mass production of small portable objects such as integrated circuit cards, for example credit cards, bank cards, payment cards for public telephones, and access cards for entering private or security areas or where payment is required, or keys having integrated circuits for the same purposes.
Known integrated circuit cards usually have a plurality of electric contact areas which can be accessed by the connector parts of apparatus in which the cards are designed to be inserted.
For some applications, such as for example the control of access to private or security areas, a card's integrated circuit may consist only of a memory which is directly connected to the contact areas by electrical conductors and which contains data that can be read, and only read, by an apparatus designed to receive the card.
For other applications, for instance where the card can be used by its holder to make payments or transactions, the circuit additionally comprises a microprocessor installed between the contact areas and the memory and which may be integrated in the same chip as the memory or in a separate chip. In this case, the apparatus with which the card may be used can not only read data in its memory but can also enter new data.
Moreover, in some cases, the various elements forming the card's electronic circuit, with the exception of the contact areas, are embedded in a body of homogeneous or composite insulating material to thereby form a module which is then inserted in a corresponding opening in the body of a card.
Aside from questions related to the integrated circuit itself (for instance what data the memory should contain, which functions should be performed by the microprocessor if one is provided, and how the memory and possibly also the microprocessor should be designed), the manufacture of the aforementioned types of integrated circuit cards involves a number of problems, in particular because of the rather numerous requirements they have to meet.
Firstly, these cards must generally have the same format as a card having a standard magnetic track, namely a length of 85 mm, a width of 54 mm and a thickness of 0.76 mm (ISO norms), or at least have close-to-standard dimensions in order to remain compact and easy to handle.
Bearing in mind: firstly, that a thickness of 760 microns corresponds roughly to only about twice the thickness of the chip of a non-protected integrated circuit; secondly, that the portion of a card's surface that can be allocated to the electronic circuit is often very limited because the major part thereof must be reserved for inscriptions such as the identification of the card-issuing entity, the card holder's identity, a signature, data needed for use and, possibly, a photo; and thirdly, that the conductor areas must be large enough to ensure a good contact with the connector members of an apparatus, it can readily be understood that standardised pre-coated, or pre-encased circuits that are at present available on the market cannot be used because they are too bulky.
To manufacture these cards or the electronic modules associated therewith it therefore becomes necessary to start with bare integrated circuit chips, fabricate the network of interconnections enabling these chips to make external electrical connections and inter-chip connections if there are several chips in the same card, and provide a protection for the assembly which is inherently very fragile especially at the junctions of conductive parts (chip connector lugs, wires, etc.)
This protection needs to be particularly effective when the cards are liable to undergo frequent and possibly large deformations due to the fact that these cards, like conventional cards, must meet quite strict norms or requirements concerning their flexibility, and the needed protection cannot be guaranteed by rigidifying the electronic modules or the areas of the cards where the circuits are situated because the flexibility requirements would no longer be fulfilled.
Furthermore, external agents like light or humidity must be prevented from deteriorating the circuit or perturbing operation.
For electronic keys which also have contact areas but are not as thin as cards and instead need to be rigid, these problems of protecting the chip(s) and the electric connections hardly occur in practice because the chips are embedded in relatively large blocks of hard plastic material which give the keys their shape.
However, there are at least two other problems that have not yet been discussed, concerning both keys and cards.
The first of these problems is that in both cases the contact areas must be designed to resist as well as possible any wear caused by the connector parts of apparatus adapted to receive the keys or cards, and frequently also they should be able to function properly even in a hostile environment such as damp or polluted air. For this reason, the areas are often formed of several superimposed layers of different metals, for example copper, nickel and gold, which obviously has the drawback of increasing the cost price of the card or key.
The second problem is that these contact areas may receive electrostatic discharges which overload the protection systems provided in the integrated circuits. When this happens, these circuits are destroyed and the cards or keys containing them are rendered inoperative.
However, there are known systems in which the transfer of data between a card and a reading or recording apparatus does not take place by electric contact as in those just discussed, but by an inductive coupling between two coils included respectively in the card and in the apparatus for receiving the card.
In these systems, the card's integrated circuit is housed in an opening provided in the card's body and the coil consists of a metal strip formed on this body using conventional printed-circuit techniques.
Thus, in this case, there are no longer any problems associated with contacts However, the problems of protecting the chip(s) and the electric connections between the various elements of the card's electronic circuit remain.
Moreover, cards of this type have at least one drawback: because of the coil their cost price is relatively high--more than the cost of most contact-type cards--and this price increases proportionally with the surface area on the card body occupied by the coil.
Of course, it is always desirable that integrated circuit cards should be as inexpensive as possible, especially cards of the throw-away type that initially have a set value paid for when the card is purchased, and that are discarded when the value has been used.